A stator (30) serving as a magnetic circuit component is manufactured by cylindrically arranging split cores (32) with windings (42) wound thereon in the direction of rotation of a rotor (50) to form a cylindrical core (32K), then, arranging a core cylinder (M3) for resin molding on the inner peripheral side of the cylindrical core (32K), and thereafter, molding the cylindrical core (32K) by resin such that a pressure of molten resin is applied in a direction of pushing the split cores (32) against the core cylinder (M3), while ends of the adjacent spilt cores (32) in the circumferential direction are freely movable to each other. Thus, in the resin molding, the split core (32) is pushed against a molding die by the pressure of the molten resin, while being freely moved. As a result, the circularity of the cylindrical core (32K) on the gap side can depend on the circularity of the core cylinder (M3), and thus can be less affected by the machining accuracy of the split cores (32).

Full Text

MAGNETIC CIRCUIT COMPONENT ELECTRIC MOTOR, FUEL PUMP, AND
MANUFACTURING METHODS THEREOF
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to magnetic circuit components, such as a stator and a rotor, which are included in an electric motor used, for example, in a fuel pump. Furthermore, the present invention relates to a method for manufacturing a magnetic circuit component, an electrical motor and a fuel pump. Description of the Related Art
As a magnetic circuit component, a cylindrical core has conventionally been known which includes a plurality of split cores arranged in the direction of rotation. Each split core has a winding wound thereon. When the magnetic circuit component is used, for example, as a stator, a rotor is disposed inside the cylindrical core. When the magnetic circuit component is used, for example, as a rotor, a rotary shaft is fixed to the inside of the cylindrical core, while a stator is disposed on the outer peripheral side of the cylindrical core.
Such a magnetic circuit component having the split cores is required to connect the split cores to each other and hold them. In a related art, an engagement portion is provided in each split core, and the engagement portions of the adjacent split cores are engaged with each other (see, for example. Patent Documents 1 to 3).
[Patent Document 1] JP-A No. 2005-204369
[Patent Document 2] JP-ANo. 2001-103690
[Patent Document 3] JP-A No. 2002-58181
Management of a gap between a stator and a rotor with high accuracy has a great influence on performance of an electric motor. Thus, it is conventionally

required to improve the circularity of the cylindrical core including magnetic circuit components.
However, in the structure with the engagement portions of the adjacent split cores engaged with each other as disclosed in Patent Documents 1 to 3, in order to improve the circularity it is necessary to improve the machining accuracy of the split core, in particular, the machining accuracy of the engagement portion. The improvement of the circularity is limited even by improving such machining accuracy.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the invention to provide a magnetic circuit component, an electric motor, a fuel pump, and manufacturing methods thereof that improve the circularity.
It is another object of the invention to provide a magnetic circuit component, an electric motor, a fuel pump, and manufacturing methods thereof that improve respective manufacturing speeds thereof.
A method of manufacturing a magnetic circuit component according to a first aspect of the invention includes the steps of cylindrically arranging split cores with windings wound thereon in the direction of rotation of a rotor to form a cylindrical core, then, arranging a molding die for resin molding on one side where a gap between a stator and the rotor is located, among the inner peripheral side and the outer peripheral side of the cylindrical core, and thereafter, molding the cylindrical core by resin such that a pressure of molten resin is applied in a direction of pushing the split cores against the molding die, while ends of the adjacent split cores in the circumferential direction are relatively movable to each other.
Thus, the split cores are integrally held by resin, which can eliminate the

necessity of the engagement portion disclosed in Patent Documents 1 to 3. In the resin molding, the split core is pushed against the molding die by the pressure of the molten resin while being freely moved. As a result, the surface on one side where the molding die is disposed, among the inner peripheral side and the outer peripheral side of the cylindrical core, that is, the surface on the side where the gap between the stator and the rotor is located is aligned by the molding die. Thus, the circularity of the surface on the side of the cylindrical core for forming the gap is less affected by the machining accuracy of the split core. For example, the size accuracy of the split core in the radial direction does not affect the circularity of the surface on the side of the cylindrical core where the gap is formed.
Because the circularity of the magnetic circuit component on the gap side can be improved, the gap between the stator and the rotor can be set with high accuracy, thereby improving the performance of the electric motor.
According to a second aspect of the invention, the magnetic circuit component may constitute the stator, and in the arranging step of the molding die, the core cylinder is inserted into and disposed on the inner peripheral side of the cylindrical core as the molding die. In this case, the magnetic circuit component is preferably used as a stator for a brushless motor which employs a permanent magnet as the rotor.
According to a third aspect of the invention, a groove extending in the direction of a rotary shaft is formed at the surface opposite to the side where the molding die may be disposed, among the inner peripheral and outer peripheral sides of the split core, and that in the molding step, the resin molding may be performed to allow the molten resin to flow into the groove. Thus, the split core can be pushed against the molding die by the molten resin flowing into the groove. This can easily achieve the resin molding in such a manner to push the split core against the molding die.

According to a fourth aspect of the invention, in the cylindrically arranging step, a jig may be used to move and arrange the split cores in the rotation direction, while holding the split cores to form the cylindrical core, and an engagement portion of the jig may be engaged with the groove to cause the split core to be held by the jig. In use of the jig for holding and moving the split cores, the groove for allowing the resin to flow thereinto as mentioned above may be also be used as the groove for engagement with the engagement portion of the jig. This can eliminate the necessity of forming a groove dedicated to hold the jig.
According to a fifth aspect of the invention, the jig may include holder units with the engagement portion corresponding to each of the split cores, and the holder units may be relatively rotatably connected to each other. In this case, in the cylindrically arranging step, the holder units holding the split cores move from a state of the split cores arranged in line to a state of the split cores arranged in the rotation direction to form the cylindrical core. This can easily form the cylindrical core in the cylindrically arranging step.
In a conventional manufacturing method, wires are wound around the respective split cores to form the windings. The split cores with the windings formed thereon are arranged in a cylindrical shape, and then the windings of the split cores of the same phase are connected by routing wires. For this reason, the work for winding the winding wire and the work for connecting the routing wire are different, which disadvantageously takes extra efforts, thus leading to a slow working speed.
For this problem, the method according to a sixth aspect of the invention further includes the steps of linearly arranging the split cores substantially in planar, and continuously winding by repeatedly performing a winding step and a routing step for each phase of the split core. The winding step includes winding a wire around the split core to form the winding. The routing step includes routing the

wire wound on the split core to another split core of the same phase to form a routing portion. In the linearly arranging step, the adjacent split cores are disposed to be apart from each other with a predetermined clearance therebetween, and in the routing step, the wire is routed so as not to cause slack in the routing portion.
In this way, in the linearly arranging step, the adjacent split cores are arranged with the predetermined clearance therebetween, and in the continuous winding step, the wire is routed so as not to cause slack in the routing portion. Accordingly, it can avoid an excessive tensile force from being applied to the routing portion in a process during which the cylindrical core is formed in the cylindrically arranging step. Also, this can avoid the occurrence of slack in the routing portion in a state in which the cylindrical core is formed. Thus, the work for winding the winding wire and the work for connecting the routing wire in the continuous winding step can be performed continuously, which can save labor for the work, thereby increasing the working speed.
A method of manufacturing a magnetic circuit component according to a seventh aspect of the invention includes the steps of linearly arranging split cores substantially in planar, then, continuously winding by repeatedly performing a winding step and a routing step for each phase of the split core, the winding step including winding a wire around the split core to form a winding, the routing step including routing the wire wound on the split core to another split core of the same phase to form a routing portion, and thereafter, cylindrically arranging the split cores in the direction of rotation of a rotor to form a cylindrical core. In the linearly arranging step, the adjacent split cores are disposed to be apart from each other with a predetermined clearance therebetween, and in the routing step, the wire is routed so as not to cause slack in the routing portion.
Accordingly, it can avoid an excessive tensile force from being applied to

the routing portion in a process during which the cylindrical core is formed in the cylindrically arranging step. Also, it can avoid the occurrence of slack in the routing portion in a state in which the cylindrical core is formed. Thus, the work for winding the winding wire and the work for connecting the routing portion can be continuously performed in the continuous winding step, thereby increasing the working speed.
According to an eighth aspect of the invention, the method of manufacturing a magnetic circuit component as described above may be applied to a method of manufacturing an electric motor to exhibit the same effect as mentioned above. According to a ninth aspect of the invention, the method of manufacturing an electric motor as described above may be applied to a method of manufacturing a fuel pump for allowing the fuel whose pressure is increased to circulate through a gap between the stator and the rotor. In this case, the gap is used as the fuel passage, and thus can be managed with high accuracy. This can exhibit the effect of managing a flow path sectional area of the fuel passage with high accuracy.
A magnetic circuit component for constituting one of a stator and a rotor included in an electric motor according to a tenth aspect of the invention includes a plurality of split cores arranged in the direction of rotation to constitute a cylindrical core, and windings wound on the split cores. The adjacent split cores are resin-molded and held without being fastened to each other.
Thus, the split cores can be integrally held by resin, which can eliminate the necessity of the engagement portion disclosed in Patent Documents 1 to 3. In the resin molding, the split core can be pushed against the molding die by the pressure of the molten resin while being freely moved. As a result, the surface on one side where the molding die is disposed, among the inner peripheral side and the outer peripheral side of the cylindrical core, that is, the surface on the side

where the gap between the stator and the rotor is located is aligned by the molding die. Thus, the circularity of the surface on the side of the cylindrical core for forming the gap is less affected by the machining accuracy of the split core. In this way, the circularity of the magnetic circuit component can be improved on the gap side to manage the gap between the stator and the rotor with high accuracy, thereby improving the performance of the electric motor.
According to an eleventh aspect of the invention, the groove extending in the direction of a rotary shaft is formed at a surface opposite to one side where the gap between the stator and the rotor is located, among the inner peripheral side and the outer peripheral side of the split core. The groove is formed to have a sectional area enlarged from an opening of the groove to a bottom thereof so as to be engageable with an engagement portion of a jig for holding and moving the split cores to form the cylindrical core. Furthermore, the groove may be filled with molded resin.
Thus, the split core is pushed against the molding die by the molten resin flowing into the groove. This can easily achieve the resin molding in such a manner to push the split core against the molding die. In use of the jig for holding and moving the split cores, the groove for allowing the resin to flow thereinto as mentioned above can also be used as the groove for engagement with the engagement portion of the jig. Accordingly, it can eliminate the necessity of forming a groove dedicated to hold the Jig.
According to a twelfth aspect of the invention, when the above magnetic circuit component is applied to an electric motor, the same effect as mentioned above can be exhibited. In a thirteenth aspect of the invention, the above electric motor may be applied to a fuel pump for allowing the fuel whose pressure is increased to circulate through the gap between the stator and the rotor. In this case, the gap is used as the fuel passage, and thus can be managed with high

accuracy, so that it can exhibit the effect of managing the flow path sectional area of the,fuel passage with high accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings. In which:
Fig, 1 is a sectional view showing a fuel pump according to an embodiment of the invention;
Fig. 2 is a sectional view taken along the line II - II of Fig. 1;
Figs. 3A to 3C are perspective views for explaining a manufacturing procedure of a stator shown in Fig. 1;
Fig. 4 is a plan view showing a manufacturing device for manufacturing the stator shown in Fig. 1;
Figs. 5A and 5B are enlarged views each showing a part of a jig of the manufacturing device in Fig. 4;
Fig. 6A is a front view showing a completed state of a winding step shown in Fig. 3C, and Fig. 68 is a side view when being viewed from the direction of arrow VIB in Fig. 6A;
Fig. 7 is a view showing a jig in Fig. 4, when being viewed from the direction of arrow VII of Fig. 6B;
Fig. 8 is a perspective view showing a state in which holder units of the jig shown in Fig. 4 are moved in an annular shape;
Fig. 9 is a perspective view showing a state of a cylindrical core formed by the movement of the holder units shown in Fig. 8;
Fig. 10 is a sectional view partially taken along the line X-X of Fig. 8;
Fig. 11 is a bottom view when being viewed from the arrow XI of Fig, 9; and

Fig. 12 is a sectional view showing a state in which the cylindrical core shown in Fig. 9 is resin-molded.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Manufacturing methods of a magnetic circuit component, an electric motor, and a fuel pump according to an embodiment of the invention will be described below with reference to the accompanying drawings. In this embodiment, the fuel pump is typically used for a fuel pump mounted on a vehicle, as an example.
First, the structure of a fuel pump 10 will be described below using Figs, 1 and 2.
Fig. 1 is a schematic sectional view of the fuel pump 10, and Fig. 2 is a sectional view taken along the line II - II of Fig. 1. The fuel pump 10 of this embodiment is an in-tank pump installed in, for example, a fuel tank of a two-wheel motor bicycle. As shown in Fig. 1, the fuel pump 10 includes a pump portion 12, a motor 13 for rotatably driving an impeller 20 of the pump portion 12, and an end support cover 28. A housing 14 encloses the outer peripheries of the pump portion 12 and the motor 13, and thus is a common housing to the pump portion 12 and the motor 13. The end support cover 28 covers the side of the motor 13 opposite to the pump portion 12 to form a discharge port 60 for discharging fuel.
The pump portion 12 is a Wesco pump including a pump cover 16, a pump casing 18, and the impeller 20. The pump cover 16 and the pump casing 18 rotatably accommodate the impeller 20 therein. The fuel drawn from a suction port 17 formed in the pump cover 16 has its pressure increased by rotation of the impeller 20, passes through a fuel passage 62 formed between the inner peripheral surface of a stator 30 and the outer peripheral surface of a rotor 50, and is discharged from the discharge port 60 formed in the end support cover 28.
The motor 13 is a brushless motor (electric motor), and includes the stator

30 (magnetic circuit component), windings 42, the rotor 50, and the like. As shown in Fig. 2, the stator 30 is constructed of six split cores 32 arranged in the circumferential direction. Each split core 32 energizes the windings 42 to generate magnetic poles on the surface opposed to the rotor 50. That is, a clearance between the inner peripheral surface of the stator 30 and the outer peripheral surface of the rotor 50 is used as the fuel passage 62 as mentioned above, and is also used as a gap 62 in the magnetic circuit between the stator 30 and the rotor 50.
The respective split cores 32 include outer peripheral portions 34 and teeth 36. Each split core 32 is constructed by integrally laminating magnetic steel plates covered with insulating films in the direction of the rotary shaft (in the direction orthogonal to the paper surface shown in Fig, 2). The outer peripheral portion 34 is formed in an arc shape with an equal width in the circumferential direction. The six outer peripheral portions 34 are formed in an annular shape. The teeth 36 each protrude from the center of the outer peripheral portion 34 toward the rotor 50 on the inner peripheral side. A resin insulating member 40 is assembled to each split core 32 so as to be apart from a winding space. A slit-like groove 35 is formed in the center of the arc-shaped outer peripheral portion 34 to extend in the direction of lamination (in the direction orthogonal to the paper suri'ace shown in Fig. 2).
The winding 42 is collectively wound onto the outer periphery of the insulating member 40 for each split core 32, and electrically connected to a terminal 44 derived to the outside of the end support cover 28 on the end support cover 28 side shown in Fig. 1. The windings 42 are classified into three kinds, namely, a U phase, a V phase, and a W phase. The driving current supplied to the winding 42 of each phase is switched by a controller (not shown) to control the magnetic pole generated in the winding 42 of each phase. In order to switch the

driving current supplied to the winding 42 to rotate the rotor 50, it is necessary to detect the position of rotation of the rotor 50. For example, preferably, the position of rotation of the rotor 50 is detected by a detection element, such as a hole element, and the driving current is switched based on the detection signal.
The rotor 50 includes a shaft 24 and a permanent magnet 54. and is rotatably set in the inner periphery of the stator 30. The shaft 24 is rotatably supported by bearings 26 and 27. As shown in Fig. 2, the permanent magnet 54 is formed in a cylindrical shape using one member, and forms eight magnetic poles in the direction of rotation. The eight magnetic poles are magnetized so as to have alternately different poles in the direction of rotation on a side of the outer peripheral surface facing the stator 30.
Now, a manufacturing method of the stator 30 that is an example of the magnetic circuit component will be described below.
1. Assembly Step of Split Core
First, press-molded magnetic steel plates are stacked and assembled in the direction of the rotary shaft (vertically as shown in Fig. 3A) to form the split core 32. Then, the insulating members 40 are respectively fitted into one end and the other end of the split core 32 as shown in Fig. 3A, In this way, the six split cores 32 with the insulating members 40 fitted thereinto are prepared.
2. Linearly Arranging Step (Planar Arranging Step)
Then, as shown in Fig. 3B, the six split cores 32 are arranged substantially in planar on line using a jig M1 shown in Fig. 4. The slit cores 32 arranged substantially in planar are disposed such that the arc-shaped end of the outer peripheral portion 34 of one split core is opposed to the arc-shaped end of the outer peripheral portion 34 of the adjacent split core 32, while these peripheral portions 34 are directed downward. In Figs. 3B and 4, the illustration of the insulating member 40 is omitted.

As shown in Fig. 4, the jig M1 has six holder units 90. The holder unit 90 includes a stopper member 91, a holder 92, a rod 93, and elastic members 94. In the linearly arranging step, the six stopper members 91 are fixed in line to a main body (not shown) of the jig Ml. The holder 92 is slidably accommodated in the stopper member 91. The holder 92 is coupled to the rod 93 to slidably move integrally with the rod 93.
Fig. 5A is an enlarged view showing a part of the jig M1 in Fig. 4. The holder 92 has an engagement portion 92a formed therein. The engagement portion 92a can be engaged with the groove 35 formed in the outer peripheral portion 34 of the split core 32. Specifically, the groove 35 is formed to have a sectional area enlarged from an opening 35a of the groove 35 to a bottom 35b thereof. The engagement portion 92a is inserted from the end surface of the groove 35 in the longitudinal direction (in the direction orthogonal to the paper surface shown in Fig. 5A) thereinto, so that the engagement portion 92a can be engaged with the groove 35. It is apparent that the shape of the engagement portion 92a and the groove 35 is not limited to the circular shape shown in Fig. 5A, and may be, for example, a trapezoidal shape as shown in Fig. 5B.
The elastic member 94 gives an elastic force in the direction of accommodating the holder 92 inside the stopper member 91, When the rod 93 is pushed against the elastic force by an external device (not shown), the engagement portion 92a of the holder 92 protrudes from the inside of the stopper member 91 to the outside thereof.
In the linearly arranging step, first, the rod 93 is pushed by the external device to cause the engagement portion 92a to protrude. In this state, the engagement portion 92a is engaged with the groove 35. Next, the external device is separated from the rod 93, and the holder 92 is drawn into the stopper member 91 by the elastic member 94. The split core 32 is drawn together with

the holder 92, whereby the outer peripheral portion 34 of the split core 32 is pushed against a stopper surface 91a of the stopper member 91 to abut against the stopper surface 91a, This fixes the split core 32 at a predetermined position.
Specifically, the six split cores 32 are arranged substantially in planar to be lined such that the adjacent split cores 32 are separated apart from each other with a predetermined clearance CL therebetween (see Figs. 4, 6Aand 6B). The term "clearance CL" as used herein means in detail the clearance between the arc-shaped end of the outer peripheral portion 34 and the arc-shaped end of the outer peripheral portion 34 of the adjacent split core 32, 3. Continuous Winding Step
Then, a winding step is performed which involves winding a wire 42N around the insulating member 40 assembled to the split core 32 using a winding machine M2 shown in Fig. 3B to form the winding 42. Then, a routing step is performed which involves routing the wire 42N wound on the split core 32 up to another split core 32 of the same phase to form a routing portion 42a. The winding step and the routing step are continuously and repeatedly performed for each of the phases (U phase, V phase and W phase) of the split core 32,
In the continuous winding step, the wire 42N is fed from a nozzle 95 of the winding machine M2, while the position of the nozzle 95 is moved to wind the wire 42 and then to route it to a predetermined position. For example, as indicated by the arrow "Y1" in Fig. 3B, the nozzle 95 is turned and moved around the split core 32 to wind the wire 42N on the insulating member 40. The routing portion 42a is routed along the outer peripheral surface of the insulating member 40.
Figs. 3C, 6Aand 68 are double-sided drawings showing a completed state of the winding step. Fig. 6A is a front view corresponding to Fig. 4, and Fig, 68 is a diagram viewed from the arrow VI8 of Fig, 6A. As mentioned above, the windings 42 are classified into three kinds, namely, the U phase, the V phase, and

the W phase. The split cores 32 are linearly arranged substantially in planar such that the (J phase, the V phase, and the W phase are positioned in line in that order. Fig. 3C shows only the winding 42 of the U phase. The reference numeral "Us" in Figs. 3C and 6A shows a winding start portion of the wire 42N of the U phase, and the reference numeral "Ue" shows a winding end portion of the wire 42N of the U phase.
Now, the functions of respective portions located between the winding start portion Us and the winding end portion Ue of the wire 42N of the U phase will be described below. That is, the winding start portion Us that starts to be wound around one split core 32 of a pair of the U-phase cores, a portion forming the winding 42 wound on the one split core 32, a bound portion 42b that is wound around and fixed to a protrusion 40a formed at the end of the insulating member 40, the routing portion 42a, another bound portion 42b that is fixed to another protrusion 40a associated with the other split core 32, another portion forming the winding 42 wound on the other split core 32, and the winding end portion Ue that is derived from the other split core 32 are constructed in this order.
In short, the nozzle 95 is moved such that the wire 42N of the U phase has the construction as mentioned above. Among the movement of the nozzle 95, the movement of the nozzle 95 in forming the winding 42 corresponds to the winding step, and the movement of the nozzle 95 in forming the routing portion 42a corresponds to the routing step. That is, the winding step and the routing step for the U phase are continuously performed as mentioned above. After completing winding of the wire 42N of the U phase as shown in Fig. 3C, the wire 42N is cut. In the same way as in the U phase, the wires 42N of the V phase and the W phase are respectively subjected to the continuous winding and routing steps. In Fig. 6A, the reference numeral "Vs" in Fig. 6A shows a winding start portion of the wire 42N of the V phase, the reference numeral "Ve" shows a

winding end portion of the wire 42N of the V phase, the reference numeral "Ws" in Fig. 6A shows a winding start portion of the wire 42N of the W phase, and the reference numera) "We" shows a winding end portion of the wire 42N of the W phase.
in the winding step during the continuous winding step, the nozzle 95 is moved, while a predetermined tensile force is applied to the wire 42N. Similarly, in the routing step, the nozzle 95 is moved with the predetermined tensile force applied to the wire 42N so as not to cause slack in the routing portion 42a. The bound portions 42b located at both ends of the routing portion 42a are fixed to the protrusions 40a, which can prevent the slack from being caused in the routing portion 42a after completion of the continuous winding step.
4. Cylindrically arranging step
Then, the six stopper members 91 fixed to the main body of the jig M1 are removed from the main body in the linearly arranging step to be brought into a state in which six holder units 90 are movable. Fig. 7 is a plan view of the jig M1 viewed from the direction of arrow "Vll" of Fig, 6B, showing the back side of the jig M1 shown in Fig. 4. As shown in Fig. 7, the six holder units 90 are rotatably connected to each other via connection shafts 96a by use of link members 96 provided in the jig M1.
In the cylindrically arranging step, as shown in Fig. 8, the six holder units 90 are moved in an annular shape. In this way, as shown in Fig. 9, the six split cores 32 are arranged in the circumferential direction to form a cylindrical core 32K.
5. Molding Die Arranging Step
Then, a molding die for applying resin molding to the cylindrical core 32K is arranged. Fig. 10 is a sectional view taken along the line X-X of Fig. 8. The molding die mainly includes a resin core cylinder M3 and a metallic outer annular

die M4. The core cylinder M3 has a columnar shape. The outer diameter of the core cylinder M3 is set to a size that is obtained by adding a gap 62 to the outer diameter of the rotor 50. The core cylinder M3 is inserted into and disposed on the cylindrical inner peripheral side of the cylindrical core 32K. The outer annular die M4 is disposed on the cylindrical inner peripheral side of the cylindrical core 32K.
Specifically, the core cylinder M3 is inserted into the cylindrical core 32K with the six holder units 90 held by the jig M1. The jig M1 is moved downward, while holding the units, causing the cylindrical core 32K to be inserted into the outer annular die M4. Thereafter, the rod 93 is pushed out against the elastic force of the elastic member 94 by an external device (not shown). The outer peripheral portions 34 of the split cores 32 pushed against the stopper surfaces 91a are opened, so that the engagement portions 92a of the holders 92 are pulled off the upper end of the groove 35 (from the upper side shown in Fig. 10). Thus, the jig Ml is removed from the cylindrical core 32K, and the core cylinder M3 and the outer annular die M4 are disposed at the predetermined positions with respect to the cylindrical core 32K. 6. Molding Step
As shown in Fig. 10, an injection gate 97 for injecting molten resin into the molding die is provided in a position opposed to the groove 35 of each split core 32 of the outer annular die M4, and positioned in the center of the groove 35 in the axial direction. That is, the six injection gates 97 are provided for pressing the molten resin from the outer peripheral surface side of the cylindrical core 32K into the molding die as indicated by the arrows Y2 shown in Fig. 10 and Fig. 11. Fig. 11 is a diagram viewed from the arrow "XI" of Fig. 9. At this time, the ends of the adjacent split cores 32 in the circumferential direction are not fastened to each other, but in a movable state. In other word, the six split cores 32 are freely

movably disposed in the radial and circumferential directions in a space 97a formed between the core cylinder M3 and the outer annular die M4 (see Fig. 10). The split cores 32 are restricted from moving in the axial direction (vertically shown in Fig. 10).
The molten resin injected from the injection gate 97 flows preferentially into the groove 35 of the split core 32 having low fluid resistance. Each split core 32 is pushed toward the center in the radial direction by the pressure of the molten resin in the groove 35. At this time, each split core 32 is freely movable in the radial and circumferential directions, and thus pushed against the outer peripheral surface M3a of the core cylinder M3 (see Figs. 10 and 11), which restricts the movement of the core cylinder M3 toward the center in the radial direction. Thus, because the six split cores 32 are molded while being pushed against the outer peripheral surface M3a of the core cylinder M3, the circularity of the inner peripheral surface 32Ka of the cylindrical core 32K (see Fig. 12) is equal to that of the outer peripheral surface M3a of the core cylinder M3.
The electrically conductive components, including the winding 42, the routing portion 42a, and the like, are covered with the molded resin, thereby preventing damage to and short-circuit of the winding 42, the routing portion 42a, and the like. The winding 42 and the routing portion 42a can be avoided from being immersed into fuel. For example, even when metallic foreign matter is contained in the fuel, the winding 42 and the routing portion 42a are prevented from being short-circuited due to the foreign matter.
As shown in Fig. 11, a protrusion M3b protruding radially outward is provided in a portion of the outer peripheral surface M3a of the core cylinder M3 located between the adjacent split cores 32. Thus, a passage enlarging portion 62a with a passage enlarged radially outward (see Fig. 2) is formed in the fuel passage 62 formed between the inner peripheral surface of the stator 30 and the

outer peripheral surface of the rotor 50. 7. Die Removing Step
Then, the outer annular die M4 and the core cylinder M3 are detached from the molded cylindrical core 32K to remove the die. Fig. 12 is a sectional view showing the cylindrical core 32K removed. In this state, the six split cores 32 are integrally held by the molded resin. The parts colored in black shown in Fig. 2 represent the molded resin, which constitutes the above-mentioned end support cover 28. Assembling the thus-formed cylindrical core 32K in contact with the inside of the housing 14 allows the cylindrical core 32K including the six split cores 32 and the windings 42 to serve as the magnetic circuit component.
As mentioned above, this embodiment will have the following effects.
(1) In the resin molding, the split core 32 is freely moved and pushed against the outer peripheral surface M3a of the core cylinder M3 by the pressure of the molten resin to be restricted from moving toward the center in the radial direction. Thus, the circularity of the inner peripheral surface 32Ka of the cylindrical core 32K is equal to that of the outer peripheral surface M3a of the core cylinder M3, regardless of the machining accuracy of the split core 32. Specifically, the circularity of the inner peripheral surface 32Ka of the cylindrical core 32K can be ensured, regardless of the press machining accuracy of the magnetic steel plates laminated to form the split core 32. That is, even if there are variations in size of the split cores 32 in the radial direction, the circularity of the inner peripheral surface 32Ka of the cylindrical core 32K can be ensured without being affected by the variations. This can manage the gap 62 in the magnetic circuit with high accuracy, which is a clearance between the inner peripheral surface of the stator 30 and the outer peripheral surface of the rotor 50, thereby improving the performance of the motor 13.
In a conventional manufacturing method which involves fastening the split .

cores 32 by welding, spatters generated in welding may be contained in the molded resin as metallic foreign matter. In this case, this may cause short-circuit of the electrically conductive components, such as the winding 42, In contrast, according to this embodiment, the fastening between the respective split cores 32 is prohibited, which can prevent occurrence of the metallic foreign matter as mentioned above, thereby avoiding the short-circuit of the electrically conductive component.
(2) In the cylindrically arranging step, the jig M1 is used to hold and move the split cores 32 to form the cylindrical core 32K. The engagement portions 92a of the jig M1 are engaged with the grooves 35 of the split cores 32 to allow the split cores 32 to be held by the jig M1. Thus, in use of the jig M1 for holding and moving the split cores 32, the groove 35 used for allowing the resin to flow thereinto as mentioned above can also be used as the groove for engagement with the engagement portion 92a of the jig M1. This can eliminate the necessity of forming a groove dedicated to hold the jig.
(3) In this embodiment, in the linearly arranging step, the adjacent split cores 32 are arranged with the predetermined clearance CL therebetween, and in the routing step, the wire 42N is routed so as not to cause slack in the routing portion 42a. This can avoid an excessive tensile force from being applied to the routing portion 42a in a process during which the cylindrical core 32K is formed in the cylindrically arranging step. Also, this can avoid the occurrence of slack in the routing portion 42a with the cylindrical core 32K formed. Thus, the work for winding the wire to form the winding 42 and the work for forming the routing portion 42a can be continuously performed, which can save labor for the work, thereby increasing the working speed.
(4) The resin insulating member 40 is immersed into the fuel, and thus may swell. When the insulating member 40 swells, the passage sectional area of

the fuel passage 62 may become small. For this matter, when the passage sectional area is intended to be ensured by simply enlarging the clearance between the inner peripheral surface of the stator 30 and the outer peripheral surface of the rotor 50 in the radial direction, the clearance serving as the gap 62 in the magnetic circuit between the stator 30 and the rotor 50 may reduce an amount of magnetic flux passing through the magnetic circuit, thus leading to reduction in performance of the motor 13.
In contrast, according to this embodiment, since the passage enlarging portion 62a is formed as mentioned above, even when the insulating member 40 swells, the passage sectional area of the fuel passage 62 can be ensured sufficiently. The passage enlarging portion 62a is located between the adjacent split cores 32, which can prevent a decrease in amount of the magnetic flux passing through the magnetic circuit.
Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.
In the above-mentioned embodiment, the rotor 50 employs the permanent magnet. When the rotor 50 is constructed of split cores 32 and windings 42, like the stator 30, this rotor 50 may be used as the magnetic circuit component. In this case, the shaft 24 is inserted into and disposed on the inner peripheral surface side of the rotor 50.
When the cylindrical core 32K constructed of the split cores 32 of the rotor 50 is subjected to the resin molding, the molten resin is pressed into the molding die from the inner peripheral surface side of the cylindrical core 32K. At this time, because each split core 32 is freely movable in the radial and circumferential directions, the split core 32 is pushed against the inner peripheral surface of the

outer annular die M4, and molded, while being restricted from' moving radially outward. Thus, the circularity of the outer peripheral surface of the cylindrical core 32K is equal to that of the inner peripheral surface of the outer annular die M4. The gap 62 in the magnetic circuit, which is a clearance between the inner peripheral surface of the stator 30 and the outer peripheral surface of the rotor 50, can be managed with high accuracy, thereby improving the performance of the motor 13.
In this case, it is preferable that formation of the grooves 35 in the inner peripheral surfaces of the teeth 36 of the split cores 32 can easily push the split cores 32 against the inner peripheral surface of the outer annular die M4 by the molten resin flowing into the grooves 35.
Although in the above-mentioned embodiment, the routing portion 42a is routed along the outer peripheral surface of the insulating member 40, the routing portion 42a may be routed along the inner peripheral surface of the insulating member 40.
Although in the above-mentioned embodiment, the electric motor including the magnetic circuit components is applied to the motor 13 of the fuel pump, the electric motor according to the invention is not limited to the electric motor for the fuel pump.
The inventors of the present application have made the invention, taking into consideration the following facts. That is, in order to improve the circularity of a cylindrical core 32K constructing of magnetic circuit components, the improvement of the circularity of a surface of the cylindrical core 32K on one side where a gap 62 between a stator 30 and a rotor 50 is positioned among the inner peripheral and outer peripheral sides of the cylindrical core 32K can manage the gap 62 with high accuracy. This can further improve the performance of an electric motor 13. In view of this point, the present invention may be provided

with the following any aspect.
, For example, a method of manufacturing a magnetic circuit component according to a first aspect of the invention includes the steps of cylindrically arranging split cores 32 with windings 42 wound thereon in the direction of rotation of a rotor 50 to form a cylindrical core 32K, then, arranging a molding die for resin molding on one side where a gap 62 between a stator 30 and the rotor 50 is located, among the inner peripheral side and the outer peripheral side of the cylindrical core 32K, and thereafter, molding the cylindrical core 32K by resin such that a pressure of molten resin is applied in a direction of pushing the split cores 32 against the molding die, while ends of the adjacent split cores 32 in the circumferential direction are relatively movable to each other.
Thus, the split cores 32 are integrally held by resin, which can eliminate the necessity of the engagement portion disclosed in Patent Documents 1 to 3. In the resin molding, the split core 32 is pushed against the molding die by the pressure of the molten resin while being freely moved. As a result, the surface on one side where the molding die is disposed, among the inner peripheral side and the outer peripheral side of the cylindrical core, that is, the surface on the side where the gap 62 between the stator and the rotor is located is aligned by the molding die. Thus, the circularity of the surface on the side of the cylindrical core 32K for forming the gap 62 is less affected by the machining accuracy of the split core 32. For example, the size accuracy of the split core 32 in the radial direction does not affect the circularity of the surface on the side of the cylindrical core 32K where the gap 62 is formed.
Because the circularity of the magnetic circuit component on the gap side can be improved, the gap 62 between the stator 30 and the rotor 50 can be set with high accuracy, thereby improving the performance of the electric motor 13.
According to a second aspect of the invention, the magnetic circuit

component may constitute the stator 30, and in the arranging step of the molding die, the core cylinder M3 is inserted into and disposed on the inner peripheral side of the cylindrical core 32K as the molding die. In this case, the magnetic circuit component is preferably used as a stator 30 for a brushless motor which employs a permanent magnet as the rotor 50.
According to a third aspect of the invention, a groove 35 extending in the direction of a rotary shaft is formed at the surface opposite to the side where the molding die may be disposed, among the inner peripheral and outer peripheral sides of the split core 32, and that in the molding step, the resin molding may be performed to allow the molten resin to flow into the groove 35. Thus, the split core 32 can be pushed against the molding die by the molten resin flowing into the groove 35. This can easily achieve the resin molding in such a manner to push the split core 32 against the molding die.
According to a fourth aspect of the invention, in the cylindrically arranging step, a jig M1 may be used to move and arrange the split cores 32 in the rotation direction, while holding the split cores 32 to form the cylindrical core 32K, and an engagement portion 92 of the jig M1 may be engaged with the groove 35 to cause the split core 32 to be held by the jig M1. In use of the jig M1 for holding and moving the split cores 32, the groove 35 for allowing the resin to flow thereinto as mentioned above may be also be used as the groove for engagement with the engagement portion 92 of the jig M1. This can eliminate the necessity of forming a groove dedicated to hold the jig M1.
According to a fifth aspect of the invention, the jig M1 may include holder units 90 with the engagement portion 92 corresponding to each of the split cores 32, and the holder units 90 may be relatively rotatably connected to each other. In this case, in the cylindrically arranging step, the holder units 90 holding the split cores 32 move from a state of the split cores 32 arranged in line to a state of the

split cores 32 arranged in the rotation direction to form the cylindrical core 32K. This can easily form the cylindrical core 32K in the cylindrically arranging step.
A method according to a sixth aspect of the invention may further include the steps of linearly arranging the split cores substantially in planar, and continuously winding by repeatedly performing a winding step and a routing step for each phase of the split core 32. The winding step includes winding a wire 42N around the split core 32 to form the winding 42. The routing step includes routing the wire 42N wound on the split core 32 to another split core 32 of the same phase to form a routing portion 42a. In the linearly arranging step, the adjacent split cores are disposed to be apart from each other with a predetermined clearance CL therebetween, and in the routing step, the wire 42N is routed so as not to cause slack in the routing portion 42a.
In this way, in the linearly arranging step, the adjacent split cores 32 are arranged with the predetermined clearance CL therebetween, and in the continuous winding step, the wire 42N is routed so as not to cause slack in the routing portion 42a. Accordingly, it can avoid an excessive tensile force from being applied to the routing portion 42a in a process during which the cylindrical core is formed in the cylindrically arranging step. Also, this can avoid the occurrence of slack in the routing portion 42a in a state in which the cylindrical core 32K is formed. Thus, the work for winding the winding wire and the work for connecting the routing wire in the continuous winding step can be performed continuously, which can save labor for the work, thereby increasing the working speed.
A method of manufacturing a magnetic circuit component according to a seventh aspect of the invention includes the steps of linearly arranging split cores 32 substantially in planar, then, continuously winding by repeatedly performing a winding step and a routing step for each phase of the split core 32, the winding

step including winding a wire 42N around the split core 32 to form a winding 42, the routing step including routing the wire 42N wound on the split core 32 to another split core 32 of the same phase to form a routing portion 42a, and thereafter, cylindrically arranging the split cores 32 in the direction of rotation of a rotor 50 to form a cylindrical core 32K. In the linearly arranging step, the adjacent split cores 32 are disposed to be apart from each other with a predetermined clearance CL therebetween, and in the routing step, the wire 42N is routed so as not to cause slack in the routing portion 42a.
Accordingly, it can avoid an excessive tensile force from being applied to the routing portion 42a in a process during which the cylindrical core is formed in the cylindrically arranging step. Also, it can avoid the occurrence of slack in the routing portion 42a in a state in which the cylindrical core 32K is formed. Thus, the work for winding the winding wire and the work for connecting the routing portion can be continuously performed in the continuous winding step, thereby increasing the working speed.
According to an eighth aspect of the invention, the method of manufacturing a magnetic circuit component as described above may be applied to a method of manufacturing an electric motor 13 to exhibit the same effect as mentioned above. According to a ninth aspect of the invention, the method of manufacturing an electric motor 13 as described above may be applied to a method of manufacturing a fuel pump 10 for allowing the fuel whose pressure is increased to circulate through a gap 62 between the stator 30 and the rotor 50. In this case, the gap 62 is used as the fuel passage, and thus can be managed with high accuracy. This can exhibit the effect of managing a flow path sectional area of the fuel passage with high accuracy.
A magnetic circuit component for constituting one of a stator 30 and a rotor 50 to be provided in an electric motor 13 according to a tenth aspect of the

invention includes a plurality of split cores 32 arranged in the direction of rotation to constitute a cylindrical core 32K, and windings 42 wound on the split cores 32. The adjacent split cores 32 are resin-molded and held without being fastened to each other.
Thus, the split cores 32 can be integrally held by resin, which can eliminate the necessity of the engagement portion disclosed in Patent Documents 1 to 3. In the resin molding, the split core 32 can be pushed against the molding die by the pressure of the molten resin while being freely moved. As a result, the surface on one side where the molding die is disposed, among the inner peripheral side and the outer peripheral side of the cylindrical core 32K, that is, the surface on the side where the gap 62 between the stator 30 and the rotor 50 is located is aligned by the molding die. Thus, the circularity of the surface on the side of the cylindrical core 32K for forming the gap 62 is less affected by the machining accuracy of the split core 32. In this way, the circularity of the magnetic circuit component can be improved on the gap side to manage the gap 62 between the stator 30 and the rotor 50 with high accuracy, thereby improving the performance of the electric motor 13.
According to an eleventh aspect of the invention, the groove 35 extending in the direction of a rotary shaft is formed at a surface opposite to one side where the gap 62 between the stator 30 and the rotor 50 is located, among the inner peripheral side and the outer peripheral side of the split core 32. The groove 35 is formed to have a sectional area enlarged from an opening of the groove 35 to a bottom thereof so as to be engageable with an engagement portion of a jig for holding and moving the split cores 32 to form the cylindrical core 32K. Furthermore, the groove 35 may be filled with molded resin.
Thus, the split core 32 is pushed against the molding die by the molten resin flowing into the groove 35. This can easily achieve the resin molding in

such a manner to push the split core 32 against the molding die. in use of the jig for holding and moving the split cores 32, the groove 35 for allowing the resin to flow thereinto as mentioned above can also be used as the groove for engagement with the engagement portion of the jig. Accordingly, it can eliminate the necessity of forming a groove dedicated to hold the jig.
According to a twelfth aspect of the invention, when the above magnetic circuit component is applied to an electric motor 13, the same effect as mentioned above can be exhibited. In a thirteenth aspect of the invention, the above electric motor 13 may be applied to a fuel pump for allowing the fuel whose pressure is increased to circulate through the gap 62 between the stator 30 and the rotor 50. In this case, the gap 62 is used as the fuel passage, and thus can be managed with high accuracy, so that it can exhibit the effect of managing the flow path sectional area of the fuel passage with high accuracy.
Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.

What is Claimed is:
1. A method of manufacturing a magnetic circuit component for
constituting one of a stator and a rotor to be provided in an electric motor, the
magnetic circuit component including a plurality of split cores arranged in a
direction of rotation and windings wound on the split cores, the method comprising
the steps of:
cylindrically arranging the split cores with the windings wound thereon in the direction of rotation of the rotor to form a cylindrical core;
arranging a molding die for resin molding at one side where a gap between the stator and the rotor is located, among an inner peripheral side and an outer peripheral side of the cylindrical core, after the cylindrically arranging step; and
molding the cylindrical core by resin such that a pressure of molten resin is applied in a direction of pushing the split cores against the molding die, while ends of the adjacent split cores in the circumferential direction are relatively movable to each other.
2. The method of manufacturing a magnetic circuit component according
to claim 1,
wherein the magnetic circuit component constitutes the stator, and wherein in the arranging step of the molding die, a core cylinder as the
molding die is inserted into and disposed on the inner peripheral side of the
cylindrical core.
3. The method of manufacturing a magnetic circuit component according
to claim 1 or 2, further comprising
forming a groove extending in a direction of a rotary shaft at a surface opposite to the side where the molding die is disposed, among the inner peripheral

side and the outer peripheral side of the split core, and
wherein in the molding step, the resin molding is performed to allow the molten resin to flow into the groove.
4. The method of manufacturing a magnetic circuit component according to claim 3, wherein in the cylindrically arranging step, a jig is used to move and arrange the split cores in the direction of rotation while holding the split cores to form the cylindrical core, and an engagement portion of the jig is engaged with the groove to cause the split cores to be held by the jig.
5. The method of manufacturing a magnetic circuit component according to claim 4,
wherein the jig includes holder units each of which is provided with the engagement portion provided corresponding to each of the split cores,
wherein the holder units are relatively rotatably connected to each other, and
wherein in the cylindrically arranging step, the holder units holding the split cores moves from a state of the split cores arranged in line to a state of the split cores arranged in the direction of rotation to form the cylindrical core.
6. The method of manufacturing a magnetic circuit component according
to any one of claims 1 to 5, further comprising the steps of:
linearly arranging the split cores substantially in planar; and
continuously winding by repeatedly performing a winding step and a
routing step for each phase of the split core, the winding step including winding a
wire around the split core to form the winding, the routing step including routing the
wire wound on the split core to another split core of the same phase to form a

routing portion,
wherein in the linearly arranging step, the adjacent split cores are disposed to be apart from each other with a predetermined clearance therebetween, and
wherein in the routing step, the wire is routed so as not to cause slack in the routing portion.
7, A method of manufacturing a magnetic circuit component for
constituting one of a stator and a rotor to be provided in an electric motor, the
magnetic circuit component including a plurality of split cores arranged in a
direction of rotation and windings wound on the split cores, the method comprising
the steps of:
linearly arranging the split cores substantially in planar;
after the linearly arranging step, continuously winding by repeatedly performing a winding step and a routing step for each phase of the split core, the winding step including winding a wire around the split core to form the winding, the routing step including routing the wire wound on the split core to another split core of the same phase to form a routing portion; and
cylindrically arranging the split cores in the direction of rotation of the rotor to form a cylindrical core, after the continuously winding step,
wherein in the linearly arranging step, the adjacent split cores are arranged to be apart from each other with a predetermined clearance therebetween, and
wherein in the routing step, the wire is routed so as not to cause slack in the routing portion.
8. A method of manufacturing an electric motor, comprising the steps of:
manufacturing one of the stator and the rotor included in the electric motor
by the manufacturing method as described in any one of claims 1 to 7;

manufacturing the other one of the stator and the rotor; and assembling the rotor to the stator.
9. A method of manufacturing a fuel pump, the fuel pump being adapted
to increase a pressure of fuel by rotating an impeller by an electric motor, and to
allow the fuel whose pressure is increased to circulate through a gap between the
stator and the rotor, the method comprising the steps of:
manufacturing the electric motor by the method as described in claim 8; and
assembling the impeller to a rotary shaft of the rotor.
10. A magnetic circuit component for constituting one of a stator and a
rotor to be provided in an electric motor, the magnetic circuit component
comprising:
a plurality of split cores arranged in a direction of rotation to constitute a cylindrical core; and
windings wound on the split cores,
wherein the adjacent split cores are resin-molded and held without being fastened to each other.
11. The magnetic circuit component according to claim 10,
wherein a groove extending in a direction of a rotation axis is formed at a surface opposite to one side where a gap between the stator and the rotor is located, among an inner peripheral side and an outer peripheral side of the split core, and
wherein the groove has a sectional area enlarged from an opening of the groove to a bottom of the groove so as to be engageable with an engagement

portion of a jig for holding and moving the split cores to form the cylindrical core, and is filled with molded resin,
12. An electric motor comprising:
the magnetic circuit component as in claim 10 or 11 for constituting one of the stator and the rotor; and
the other one of the stator and the rotor.
13. A fuel pump comprising:
the electric motor as in claim 12; and
an impeller adapted to rotate together with a rotary shaft of the electric motor, thereby increasing a pressure of fuel,
wherein the fuel having an increased pressure is allowed to circulate through a gap between the stator and the rotor of the electric motor.